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How Much Do You Think Being On 910 kHz With The Whistle Hurt Over The Years?

S

Schroedingers Cat

Has anyone ever quantified how much of a disadvantage being on 910 KHz, with the IF Harmonic/Oscillator/Image whistle, was? It's sort of moot with most modern receivers with PLL tuning. Before NARBA in 1941, there were no stations on 910 that I know of in the US, because it was a Class I-A or I-B Canadian and/or Mexican Clear Channel. Regional frequency stations moved from 880 to 910 in 1941, and the Canadian and/or Mexican Clear Channels moved from 910 to 940. Suddenly, a few dozen stations were affected with the whistle, and more after the War. I don't think many IFs were retuned, but perhaps David or Frank or the rest may know.
 
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Schroedingers Cat said:
Has anyone ever quantified how much of a disadvantage being on 910 KHz, with the IF Harmonic/Oscillator/Image whistle, was? It's sort of moot with most modern receivers with PLL tuning. Before NARBA in 1941, there were no stations on 910 that I know of in the US, because it was a Class I-A or I-B Canadian and/or Mexican Clear Channel. Regional frequency stations moved from 880 to 910 in 1941, and the Canadian and/or Mexican Clear Channels moved from 910 to 940. Suddenly, a few dozen stations were affected with the whistle, and more after the War. I don't think many IFs were retuned, but perhaps David or Frank or the rest may know.
Click to expand...

I don’t notice the whistle on 910 AM here in Phoenix, Arizona since we have a local, KGME, but I do notice the whistle on 1260 AM. It’s so bad that it can drown out the semi-local station from Apache Junction, KBSZ-AM. I have also noticed it on 1130 AM up in the Pacific Northwest around Seattle when I try to listen to CKWX from Vancouver, BC.
 
Maybe you have only been using newer radios. Car radios used to use a 262 kHz IF, but almost all other radios used 455 kHz. It's generally explained as the 2X harmonic, but there may be other theories.
 
Schroedingers Cat said:
Maybe you have only been using newer radios. Car radios used to use a 262 kHz IF, but almost all other radios used 455 kHz. It's generally explained as the 2X harmonic, but there may be other theories.
Click to expand...
It isn't a theory, as everyone who grew up in San Francisco or in my case, Portland OR are well aware! Every time you had to tune the radio to 910, the heterodyne squeal jumped right out at you!
 
When I worked (part-time, while in the Navy) at WPTX, the whistle on 920 was pretty noticeable. I always wanted a McKay-Dymek tuner, with the 10K notch filter, to see if that would help. They are now on 1690.

KALL-910, later KWDZ, here in SLC didn't seem terrible. I heard it on my 1970's Pioneer stereo, but the Denon TU-680, the "NAB SuperTuner" seemed to filter it out. Maybe the NRSC filter curves?? KALL did OK in the ratings.
 
My local station on 910, WSUI, used to have a noticeable whistle. I remember hearing it mostly at night, when the station had a good jazz show. I got used to it. I haven't heard a whistle on WSUI in years however.
 
The theory I mentioned is that some people said it was the oscillator that produced the whistle as a difference frequency which interfered with the 455 kHz, not just a harmonic doubling. No doubt there is a whistle.
 
Digitally tuned receivers usually use a 450 kHz IF instead of 455 kHz, but are also usually better filtered, so you won't hear a whistle on 900 kHz AM.
 
whistle radio

Schroedingers Cat said:
Has anyone ever quantified how much of a disadvantage being on 910 KHz, with the IF Harmonic/Oscillator/Image whistle, was? It's sort of moot with most modern receivers with PLL tuning. Before NARBA in 1941, there were no stations on 910 that I know of in the US, because it was a Class I-A or I-B Canadian and/or Mexican Clear Channel. Regional frequency stations moved from 880 to 910 in 1941, and the Canadian and/or Mexican Clear Channels moved from 910 to 940. Suddenly, a few dozen stations were affected with the whistle, and more after the War. I don't think many IFs were retuned, but perhaps David or Frank or the rest may know.
Click to expand...

Growing up in the SF Bay area, we were always listening to then KNEW, 910 AM as that was the country station my dad loved.. The analog tuned radios we had (except for the cars) all had the 455 2nd harmonic whistle problem. Even if you zero beat the whistle, most radio were just not stable enough to remain exactly on freq, and would drift slowly and you would hear the whistle creeping up in frequency... Drove dad nuts.
 
jammerdave said:
Growing up in the SF Bay area, we were always listening to then KNEW, 910 AM as that was the country station my dad loved.. The analog tuned radios we had (except for the cars) all had the 455 2nd harmonic whistle problem. Even if you zero beat the whistle, most radio were just not stable enough to remain exactly on freq, and would drift slowly and you would hear the whistle creeping up in frequency... Drove dad nuts.
Click to expand...

But the OSCILLATOR was what drifted, not the IF. I'll have to sit down and figure that out.
 
Schroedingers Cat said:
But the OSCILLATOR was what drifted, not the IF. I'll have to sit down and figure that out.
Click to expand...

If the radio was tuned exactly to the 910 kHz station, the oscillator was running at 1365 kHz. The signal input (difference between the two) to the IF stage was at 455 kHZ, with the harmonic at 910 kHz - zero beat.

It the oscillator drifted to 1366 kHz, the signal input to the IF stage was 456 kHz, with the harmonic at 912 kHz.

If the oscillator drifted to 1367 kHz, the signal input to the IF stage was 457 kHz, with the harmonic at 914 KHz.

So the IF harmonic frequency changed by double the change in the oscillator frequency.
 
910 here in Charleston (ESPN sports) has an issue, especially during the daytime. The sound on the signal sometimes makes it hard to hear. The sound of the signal can be tinny, especially the further you get from the transmitter.

That’s why they started an FM translator on 94.7.
 
kevtronics said:
Digitally tuned receivers usually use a 450 kHz IF instead of 455 kHz, but are also usually better filtered, so you won't hear a whistle on 900 kHz AM.
Click to expand...

I think that's the case with some of my digitally tuned, PLL radios (as well as the DSP models). The combination of the 450 khz or so IF and the narrow filtering reduces or eliminates the whistle.
 
Please forgive any tangent from the topic ; I just felt prodded to add a few notes.

The DXing crew, as Queens NYC schoolkids back during those Easter week escapes, used the days to vacation and clean-out this house south of Kingston NY for summer use each year. The usual stuff .... cutting the grass (if any) .... airing out the place .... stickball ....planting tomatoes .... subsisting on bologna sandwiches .... occasional shoplifting .... cleaning and painting ..... and naturally, DXing.
WKNY 1490 Kingston was the loudest station. They also put a wicked signal, complete with squeal, on 580. That, of course, was the result of 2 X 455 (910) subtracted from 1490. At the time, we didn't know why this was so. The standard-issue 'house' radio was a Stromberg-Carlson, btw.

Some years later, my Folks moved to Fairless Hills/Levittown PA. The loudest station there was WBCB 1490, with its one tower not even a mile from the house. WBCB dutifully put a loud signal onto 580, whistle and all. The Folks had some sort of Sanyo-ish stereo receiver and sound system in the living room. It was impossible to center WBCB's '580 signal' without that whine. It was as loud as WFIL 560.
 
I started a thread once about stations who moved from the Top of The Dial to the IF Image Frequency, or near it. One was CFOS 1470 kHz Owen Sound, ON, which moved to 560 kHz. A close one was WMIC 1560 kHz Sandusky, MI, which moved to 660 kHz.
 
When KIXI Seattle was at 910 (get it, "IXI" in roman numerals is sort of 91?) they used to refer to the whine on air as the "KIXI Whistle." Pronounced "Kicksie Whistle", kind of cute. Bet they were glad to move to 880, though!
 
The New Chico said:
When KIXI Seattle was at 910 (get it, "IXI" in roman numerals is sort of 91?) they used to refer to the whine on air as the "KIXI Whistle." Pronounced "Kicksie Whistle", kind of cute. Bet they were glad to move to 880, though!
Click to expand...
I'm sure they were. 50KW tends to be better than 1KW!
 
We had a problem on Miami Beach where the Miami Marine operator was on 2490 and the top-forty WSRF (SuRF) was on 1580.
2490-910=1580.
 
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